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Old 07-21-2005, 11:59 AM   #15
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You actually have two problems: Some electrical device is shorted to the skin, and your skin is not grounded like it should be.

Fix the ground problem first. After it is fixed, the good ground will probably cause the offending device to either pop a breaker or blow a fuse.

A strict definition of polarity only involves the hot & neutral wires. If they are crossed, the light comes on. Although I have not seen Pahaska's device, there is a good chance that it checks polarity with respect to hot, neutral, AND ground. If John were to plug his device into your trailer, I am willing to bet the "bad ground" light would be illuminated.

Also, your light is probably off because of a bad ground. A good ground is required for it to work at all.

Tom
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Old 07-21-2005, 04:05 PM   #16
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Polarity Light Works

Thank you. The polarity light works. When I rotated the plug 180 degrees and reinserted the plug the light went out. Also the skin stopped tingling.

Evidently the hot and neutral when reversed can cause the hot to go to ground. Because I see my electric line into the house with one line going to ground, the other I assume is hot.

I wonder if this polarity could fry electronics?
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Old 07-21-2005, 04:57 PM   #17
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If you can rotate anything electrical 180 deg & reinsert it on an Airstream, then someone did a poor job of whatever electrical repair they set out to do.

For safety's sake, I personally think you should return your electrical connection to an "as delivered" condition. If you choose not to, then mark your connections in their "non-shocking" state so you can reconnect them the right way in the future.

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Old 07-21-2005, 06:21 PM   #18
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The neutral and ground are probably connected somewhere in the trailer - so reversing the plug (which you should not be able to do!) made both the neutral and ground hot. Normally this would create a short through the ground of your three prong plug, tripping the campground breaker. That you could reverse the plug, and energize the skin without tripping the breaker, suggest that the third prong on your plug is missing. Fix it before someone gets hurt!

A regular circuit breaker will not trip to save you under this scenerio. A ground fault interrupter (GFI) breaker compares the currrent from the hot with the return, tripping if there is a discrepancy. A GFI would trip under the circumstances described here.
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Old 07-21-2005, 06:55 PM   #19
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Bad assumption

Quote:
Originally Posted by dmac
The neutral and ground are probably connected somewhere in the trailer ...
No. They are not.

At face value, why run two separate wires just to twist them together?

In fact, this statement bothered me enough to go out to my Airstream, and remove the breaker box cover, and inspect the wiring. The ground, and neutral wires are on separate busses isolated from each other.

Sure, I inspected a 38 year old breaker box. But the electrical code has only gotten more tough as time passes. There is no reason to think anyone with a later model Airstream has anything different.

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Old 07-21-2005, 09:51 PM   #20
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Bingo, Light Bulb Goes On, Reversed Polarity Light Off

Yes, I understand, many thanks.

The ground pin was removed by PO allowing the reverse polarity, probably to use a non-grounded cord. The reversed polarity caused the neutral (which may also be routed to ground like the power lines to my house) to be hot. In the absence of a ground by way of the power cord the hot body ground seeks the path of least resistance. Hence ther tingling door.

This explains a lot of my confusion. I appreciate the help.
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Old 07-22-2005, 12:45 PM   #21
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I still believe the neutral and the ground are connected somewhere in the trailer - but not necessarily in the trailer's breaker box. For example, an appliance may have them common. You can check a trailer easily with an ohmmeter - check the resistance between neutral and ground on the main plug.

I realize this may not make sense why two wires are run that are connected together. Your home breaker box has neutral and ground connected in the box, yet all those redundant wires are run all the way back to it! The neutral goes to ground, and the ground is an alternate path to ground. The idea is to have conduit, appliance chassis, light fixture trim, etc grounded through a second path so if there is a short between hot and these parts the path is to ground and not to a person, and the breaker will overload and trip. The second path provides a level of redundancy to the system!
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Old 07-22-2005, 12:57 PM   #22
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dmac,

I owe you an apology. I took your earlier post to mean that the Airstream came from the factory with the two wires twisted together. I now see that you meant someone else had done it.

Unfortunately, Fast Dan has not indicated he plans to fix his multi-position connector. An unsafe condition will exist in his Airstream until that occurs.

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Old 07-22-2005, 01:04 PM   #23
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My faded memory recalls seeing appliances where neutral and ground are both attached to the appliance chassis, if correct then his trailer may have come from the factory this way. In any case, the plug on the main electrical cord must be replaced. That tingling sensation could be fatal with rain and bare feet!
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Old 07-22-2005, 02:30 PM   #24
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Isolation transformer

You could use an isolation transformer which would eliminate the tingling problem completely. Problem is that they are expensive, heavy and finding a location to put the darn thing would be a problem. But it would guarantee that no matter where you were or what you plugged in to, you would be golden.
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Old 07-22-2005, 04:07 PM   #25
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Quote:
Originally Posted by dmac
My faded memory recalls seeing appliances where neutral and ground are both attached to the appliance chassis, if correct then his trailer may have come from the factory this way...
I believe what you are recalling applied to your home's 220 vac stove. If you had an oven light, which ran on 120 vac, the neutral leg was tied to ground. An electric dryer's motor was the same way.

For a purely 120 vac application such as an Airstream, there is no reason to tie neutral & ground together anywhere in the trailer.

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Old 07-22-2005, 10:51 PM   #26
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Believe me, connecting a ground and neutral together will trip the campground breaker. My incident 3 years ago where a short in the 30 amp plug kept tripping the campground breaker brought the services of a well meaning factory maintenance man to my trailer. When I wasn't looking, he ran a jumper wire from neutral to ground which is acceptable in the factory where he worked. Unfortunately this kept tripping the GFIC of the campground as well as the GFIC in my garage when I got home even after I replaced the offending plug. Only comparing the wiring in my breaker box to the wiring diagram in my manual revealed the culprit. As soon as it was removed everything was back to normal.

I don't think this is the same thing that you have going on but the ground/neutral caught my eye.
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Old 10-16-2005, 12:47 AM   #27
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Dan,
I haven't checked my Airstream to see, but I suspect that the 120 volt system is wired the same as a house system. If that's the case, then the neutral wires and the ground wires are connected to each other in the main power distribution box. This is the only place where they are supposed to be interconnected.


Craig,
Connecting the neutral wire to ground outside the distribution box will not trip the circuit breaker, but it should trip a GFI (Ground Fault Interrupter). The GFI compares the current between the hot (black) and the neutral (white) wires. If this current is not equal, then current is leaking to ground somewhere and it will shut off the circuit. A straight circuit breaker will trip only when the current through the breaker exceeds its rating.

Rob,
Yes, you do understand it. I'm glad you got it all figured out before you or anyone else got hurt. I'm not an electrician by trade, but I know enough about it to understand that many people who think they can wire a circuit can't. One of the most common problems is that unknowing amateurs don't know that polarity matters on AC circuits.

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Old 10-16-2005, 06:04 AM   #28
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. . . .
I haven't checked my Airstream to see, but I suspect that the 120 volt system is wired the same as a house system. If that's the case, then the neutral wires and the ground wires are connected to each other in the main power distribution box. This is the only place where they are supposed to be interconnected.
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Loren,

You should check, because an RV is not wired the same as your house. The ground and neutral should not be connected at the main power distribution box on your airstream.

The reason is that you do not have a real 'ground' at your campsite, unless you pound a 10 ft rod into the ground. The way you get to a real ground is through the power pedestal, which connects to ground through the park's power system.

Many residential electricians are caught unaware by this. If you have an electrician work on your trailer be sure he/she understands what a 'floating ground' is.
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